1. Field of the Invention
This invention relates to a novel method for removal of oil or asphalt from surfaces of inorganic particles having pigment in an outer layer thereof with a non-chlorocarbon solvent comprising a mixture of monocyclic terpene and aliphatic petroleum distillates. The method is especially applicable to the deoiling of roofing granules having pigment in an outer ceramic coating thereon.
2. Description of the Related Art
Inorganic particles having pigments present in an outer layer thereof, such as naturally and artificially color-coated granules, are ubiquitous in the roofing and siding industry. Exemplary applications thereof are in granular surfaced bituminous roll roofing and asphalt shingles. The granules, as partially embedded in one surface of asphalt-impregnated and asphalt-coated fiber sheet material, form a coating to provide an inherently weather-resistant and decorative exterior surface.
Typically, and as explained, e.g. in U.S. Pat. No. 3,528,842, colored inorganic particles used as roofing and siding granules are manufactured by coating a crushed mineral or rock granule substrate with a suitable pigment to form a ceramic bond. The coating is formed from a solublized silicate solution which is insolublized either by heat treatment or a combination of heat treatment and chemical action to a substantially water-insoluble state and is strongly adherent to the base granule. In carrying out these methods the pigment is typically uniformly applied to the granular surface with the soluble silicate solution, and the silicate is insolubilized as noted above in the presence of an acidic material or clay. Other patents which are representative of the state of the art in making pigmented granules include U.S. Pat. Nos. 2,111,131; 3,255,031 and 3,507,676.
In any event, oil, such as naphthenic slate oil, is typically used during the production of such roofing granules as a carrier for treatments, e.g. as an adhesion medium, and for dust-suppression. This oil temporarily remains on the surface portions of the finished roofing granules after processing is completed. This residual surface oil often can effectively change the color or chroma of the granules. However, the oil is eventually removed from the granules as a result of natural weathering once the granules are put into service and exposed to the elements. This loss of oil effects an apparent color change in the granules, which is instrumentally and visually discernible. This color change can occur in a relatively short period of time once the granules are put into service, e.g. after only two weeks to three months.
As can be understood, the deoiled color of the granules is of greater interest and relevance to all concerned in selecting a color of granule to be put into service than the temporary oiled color as it represents the ultimate permanent color of the shingled roof, and the like.
Therefore, for quality control in the roofing industry, manufacturing specifications for granule color are determined industry-wide on a "deoiled" basis of the production samples of colored granules. Techniques for removing oil from the granules have been proposed and used in the field. Since it is inefficient for a roofing granule manufacturer to use natural weathering to ascertain the deoiled color of a particular produced batch of granules, organic solvents typically have been used to readily remove oil from production samples of granules to determine their deoiled color and ascertain whether such conforms to industrial standards on color grades before the product is released into the market.
For instance, one widely-accepted procedure for determining the true color or deoiled color of produced granules involved the use of a chlorocarbon solvent, namely 1,1,1-trichloroethane. For example, in one standard procedure using 1,1,1-trichloroethane as a deoiler for pigmented roofing granules, a sample of oiled granules was first screened to Tyler mesh size -14/+20 (US Standard -16/+20). The screened sample was then placed in a 100 milliliter beaker, the granules filling up to 50 milliters of a beaker. The beaker was then filled to the rim with 1,1,1-trichloroethane. The granules and 1,1,1-trichloroethane were then allowed to sit undisturbed for about five minutes. The granules and trichloroethane were then poured into a deoiling funnel and the solvent drained without stirring into a one gallon can. Next, the funnel was filled with distilled water to the rim and stirred while draining, being sure to collect all solvent and water for proper disposal. The remaining granule samples in the funnel were placed on a white paper towel and dried in a vented oven. As to the temperature of the drying oven, temperatures ranging from about 80.degree. C. to about 110.degree. C. are suitable, and the samples merely needed to be taken out when dry. However, the temperature of the drying oven also could be set at 150.degree. C. Finally, the dried granules were cooled on paper towels to room temperature on a table top prior to making any color determinations. Then, to analytically determine the color of the deoiled granules, the granules preferably have a L*a*b* delta compared with a standard granule of +/-1.0.
The L*a*b* color space test is discussed in greater detail herein. Briefly, a sample of deoiled granules is placed in a machine fitted with a defined light source and the reflectance from the sample recorded on three different color scales according to the "opponent-colors" scales. The opponent color scales give measurements of color in units of approximate visual uniformity throughout the color solid. In general, "L*" measures lightness and varies from 100 for perfect white to zero for black, approximately as the eye would evaluate it. The parameters "a*" and "b*", the chromatacity dimensions, give understandable designations of color as follows: a* measures redness when plus, gray when zero and greenness when minus; b* measures yellowness when plus, gray when zero and blueness when minus.
However, the past use of chlorocarbons solvents, and especially 1,1,1-trichloroethane, for deoiling granules, although satisfactory and widely used for deoiling per se, now has serious drawbacks. As now widely acknowledged, chlorocarbons contribute to the depletion of the earth's ozone layer. In fact, international committments have been made under the Montreal Protocol to phase out the production and use of chlorocarbons. Therefore, industries have been urgently seeking effective alternatives to the obsolescent chlorocarbons, including chlorocarbon solvents such as 1,1,1-trichloroethane.
However, the roofing granule industry has acquired a substantial body of knowledge and experience on the deoiling action and color space test attributes of pigmented inorganic particles deoiled by 1,1,1-trichloroethane. Therefore, it would be highly desired and less traumatic for the roofing and siding particle industry if a replacement could be identified for 1,1,1-trichloroethane which not only correlates well with natural weathering but which also has deoiling performance akin to its predecessor 1,1,1-trichloroethane.
In general, a large number of substitutes for chlorocarbon liquid solvents have been proposed in recent times. For instance, T&R Chemicals Inc. proposes certain para-menthadienes formed in a process from pine tree turpentine as a solvent material, designated MSOL, as general substitute for chlorocarbon solvents. This MSOL solvent, in turn, is said to be an effective alternative to a competing non-chlorocarbon solvent of citrus limonene (d-limonene) produced in the orange juice processing industry, which, in some cases, depending on the predilections and olfactory sensitivity of the user, is characterized as having a strong overpowering odor.
Also, Bush Boake and Allen, a Union Camp Corporation, has advertised a solvent designated BBA Solvent 401 (or 411) as a terpene-derived solvent specifically designed for use in a newly-developed cleaning process for electronic and precision engineering components, which is said to be an environmentally responsible alternative to the use of CFC's and chlorinated hydrocarbons. This company also advertises a solvent designated BBA Solvent K102, which is said to be a proprietary degreasing mixture of terpene hydrocarbons (p-menthadienes) and terpene alcohols useful for a wide range of industrial cleaning processes with low environmental impact.
Another solvent that is touted as containing no chlorinated hydrocarbons or petroleum distillates is designated ZEP BIG ORANGE.TM., a naturally occurring citrus solvent made by Zep Manufacturing Company. ZEP BIG ORANGE.TM. solvent is said to be an industrial degreaser for motors, engine parts, etc. and industrial parts, a tar and asphalt emulsifier, a good cleaner for unpainted concrete which may damage painted surface and an excellent grafitti remover. Another solvent advertised by Zep Manufacturing Company as having no chlorinated solvents such as 1,1,1-trichlorethane is ZEP C-SOLV.TM., which is said to be useful for degreasing operations such as tank cleaning and electric motors.
Also, West Penetone advertises a safer degreaser than 1,1,1-trichloroethane designated CITRIKLEEN.RTM. XPC, which is non-chlorinated and nonpetroleum based, and said to be used for removal of carbon black, graphite, liquified polymers, tar, asphalt, greases and oils from hard metal and non-metal surfaces.
PT Technologies, Inc. advertises a solvent designated PF.TM. Degreaser as a replacement for harmful solvents such as 1,1,1-trichloroethane, freon, methyl ethyl ketone, acetone, mineral spirits. PF.TM. Degreaser is said to be useful for industrial applications where a 100% volatile solvent is preferred and can be used to remove hydrocarbon, silicone, or polyethylene based greases, oils, tars and gels. The PF.TM. Degreaser solvent is said to have passed common carrier aircraft metals compatibility testing, and is said to be safe to use prior to painting, and on painted surfaces.
However, the deoiling action that any given solvent may have on a pigmented ceramic-coated granule is highly unpredictable. That is, the solvent used must deoil the surface regions of granules in a relatively consistent repeatable manner, e.g., in terms of the color space test readings taken on the deoiled granules, and without freeing or leaching pigments from the granules or otherwise permanently disturbing the unique and specific morphology and composition of the granules and their surface coating(s). Importantly, the deoiling effected by the solvent used to deoil the granules must correlate well with deoiling caused by natural weathering in order to provide an accurate and reliable predetermination of whether the pigmented granules are either inside or outside industry specifications. Also, the solvent must be relatively safe to handle such as in terms of its flammability, noxiousness and pungency.
None of the above literatures specifically describe an application of a nonchlorocarbon solvent towards meeting the peculiar requirements arising in and associated with deoiling pigmented inorganic particles, and especially pigmented ceramic-coated inorganic particles for grading purposes, and the industry has urgently awaited for and would place value on such a discovery.